A new method to map groundwater potential at a village scale, based on a comprehensive borehole database. An application to Sikasso, Republic of Mali. Ana Carolina Gonçalves Delgado Mestrado em Geologia Departamento de Geociências, Ambiente e Ordenamento de Território 2017/2018 Orientador Jorge Espinha Marques, Professor Auxiliar, Faculdade de Ciências da Universidade do Porto Coorientador Pedro Martinez Santos, Professor Titular, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid Todas as correções determinadas pelo júri, e só essas, foram efetuadas. O Presidente do Júri, Porto, ______/______/_________ FCUP 3 A new method to map groundwater potential at a village scale, based on a comprehensive borehole database. An application to Sikasso, Republic of Mali. Acknowledgements I would like to express my deep sense of gratitude to Prof. Pedro Martinez Santos for the invaluable support, continuous guidance and for providing me the opportunity to embark on this project which started in Spain. To Prof. Jorge Espinha Marques I would also like to thank for his valuable advice and excellent guidance trough the development of this dissertation. I am thankful to all the people who helped me directly or indirectly to complete this thesis. Last but not the least I would like to thank my family for all the support provided not only during the writing of the thesis but also throughout all my time in University. FCUP 4 A new method to map groundwater potential at a village scale, based on a comprehensive borehole database. An application to Sikasso, Republic of Mali. Abstract in portuguese O principal objetivo da presente Dissertação foi a elaboração de um mapa de potencial das águas subterrâneas para a região de Sikasso, na República do Mali, com base nos mesmos parâmetros utilizados num estudo prévio, mas para todo o país e uma posterior comparação e análise dos mesmos, de forma a clarificar a importância e relevância deste tipo de estudo a escalas mais localizadas. Para tal, criou-se uma base de dados com os poços tradicionais e os furos existentes em Sikasso e sua respetiva informação. Para tratamento desta mesma base de dados e para a elaboração de mapas temáticos e de potencial das águas subterrâneas utilizou-se o software QGIS. A tese foi desenvolvida, numa fase inicial, em Espanha, entre setembro de 2017 e janeiro de 2018, em colaboração com a Universidad Complutese de Madrid (inserida no programa Erasmus +) e terminada em Portugal, na Universidade do Porto, a setembro de 2018. Palavras-chave: Água subterrânea, potencial da água subterrânea, Sikasso, QGIS. FCUP 5 A new method to map groundwater potential at a village scale, based on a comprehensive borehole database. An application to Sikasso, Republic of Mali. Abstract in English The main goal of this thesis was the elaboration of a groundwater potential map for the Sikasso region, in Republic of Mali, based in the same parameters used in a previous study but for all country, and a later comparison and analyses of them, aiming to clarify the importance and relevance of this type of study at smaller scales. For that, a database was created with the location of the traditional wells and boreholes and its information. To treat this database and develop the thematic and groundwater potential maps the open source software QGIS was used. This thesis was developed initially in Spain, between September 2017 and January 2018, in colaboration with Universidad Complutense de Madrid (as part of an Erasmus+ program) and was completed in Portugal, in Porto University, in September 2018. Keywords: Groundwater, groundwater potential, Sikasso, QGIS. FCUP 6 A new method to map groundwater potential at a village scale, based on a comprehensive borehole database. An application to Sikasso, Republic of Mali. Table of contents Acknowledgements ....................................................................................................... 3 Abstract in portuguese .................................................................................................. 4 Abstract in English ........................................................................................................ 5 Table of contents .......................................................................................................... 6 List of figures ................................................................................................................ 7 List of tables ................................................................................................................. 9 1.Introduction .............................................................................................................. 10 2.Study area ............................................................................................................... 13 2.1 Climate .............................................................................................................. 13 2.2 Geology ............................................................................................................. 15 2.3 Hydrogeology .................................................................................................... 22 2.4 Borehole database ............................................................................................ 25 3. Hydrogeological parameters ................................................................................... 26 4. Methods and procedures ........................................................................................ 27 4.1 Database ........................................................................................................... 27 4.2 QGIS analyses .................................................................................................. 28 5. Results and discussion ........................................................................................... 30 6. Conclusions ............................................................................................................ 41 FCUP 7 A new method to map groundwater potential at a village scale, based on a comprehensive borehole database. An application to Sikasso, Republic of Mali. 7. Bibliography ............................................................................................................ 43 8. Appendix ................................................................................................................. 47 List of figures Figure 1-Average annual rainfall in Mali between 1971 and 2000 . ................................. 14 Figure 2-Sikasso precipitation (mm) ...................................................................................... 14 Figure 3-Mali´s main geological units .................................................................................... 16 Figure 4- Yafolila, Morila and Syama belts ........................................................................... 17 Figure 5-Geological simplified from Sikasso. Modified from ............................................. 19 Figure 6-Mali´s aquifers. .......................................................................................................... 23 Figure 7- Geographical location of the Klela Basin ............................................................ 24 Figure 8-Long-term annual recharge in the Klela Basin ..................................................... 24 Figure 9-Location of the boreholes in the study area. ........................................................ 26 Figure 10-Borehole success rate thematic map. ................................................................. 30 Figure 11-Borehole yield thematic map. ............................................................................... 31 Figure 12-Borehole depth thematic map. ............................................................................. 33 Figure 13-Electrical conductivity thematic map. .................................................................. 34 Figure 14-Location of the highest electrical conductivity value. ........................................ 35 Figure 15-Borehole success rate thematic map based on the new breaks. ................... 36 Figure 16-Borehole depth thematic map based on the new breaks. ................................ 36 FCUP 8 A new method to map groundwater potential at a village scale, based on a comprehensive borehole database. An application to Sikasso, Republic of Mali. Figure 17-Commune scale and village scale groundwater potential maps. Commune scale map adapted from .......................................................................................................... 38 Figure 18-Areas with not enough data. ................................................................................. 39 Figure 19-A-Groundwater potential map and B- Geological map from the western part of Sikasso adapted from (Sandy, 2017). .............................................................................. 40 Figure 20-Database sheet provided by DNH. ...................................................................... 47 Figure 21-Part of the attribute table organized database. .................................................. 48 Figure 22-Sikasso and study area (Sikasso + borders) ..................................................... 49 Figure 23- Borehole success rate grid produced with Surfer 11, with the kriging method. ....................................................................................................................................................